1. A 1 ?, 25kVA, 220/440, 60 Hz transformer gave the following test results:
Open circuit test (440V side open): 220V, 9.5A, 650W
Short circuit test (220 V side shorted): 37.5V, 55A, 950W
a) Derive the approximate equivalent circuit (respect to either side) (10)
b) Determine the voltage regulation at 90% load, 0.8 PF lagging. (10)
c) Draw the phasor diagram for condition (b). (5)
d) Efficiency of the transformer for condition (b). (10)
e) (Bonus) What is the load KVA for maximum efficiency and the maximum efficiency at
0.9 power factor. (5)